Larval dispersal between hydrothermal vent habitats

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 1996.Includes bibliographical references.by Stacy L. Kim.Ph.D

Why Referees Stay in the Game

Current trends indicate the number of qualified sports officials continues to dwindle. Therefore, this research sought to better understand reasons for initial entry, continuation, and potential discontinuation with officiating, while also identifying problematic issues, and potential solutions. Content analysis was utilized to examine five open-ended online survey responses from 2,485 referees. The results indicate that Enjoyable Affiliation (58%) and Remuneration (14%) were key to referees becoming involved in officiating. Those two themes, Enjoyable Affiliation (75%) and Remuneration (14%), were also identified as important to retaining officials. Physical Limitations were mentioned by 58% of the respondents regarding why they plan to discontinue. In terms of the most problematic issues, referees most frequently indicated Abuse (42%) and Administrative Issues (20%). Lastly, findings suggest the best ways to recruit and retain officials are to Provide Mentors and Training (32%), Market to Young People (23%), and Increase Pay (19%). Practical implications and strategies that include attracting more women, underrepresented ethnicities, and young people into sports officiating are provided

Development of the Referee Retention Scale

Building upon the current sport officiating research, this study puts forth the Referee Retention Scale (RRS). Through a three-phase process, the researchers developed a valid and reliable scale to predict sport officials’ job satisfaction and intention to continue. The first phase consisted of instrument development, while the second phase included field testing of referees (n=253). After EFA and Rasch analysis, the resultant refined scale from phase 1 and 2 was then administered to 979 referees in phase 3. Phase 3 results using CFA indicated that the 7-factor, 28-item RRS was a valid and reliable tool for measuring and predicting referee retention. The results highlight the importance of considering a variety of factors associated with the referee experience, which include Administrator Consideration, Intrinsic Motives, Mentoring, Remuneration, Sense of Community, Lack of Stress, and Continuing Education. A discussion on how the RRS can help administrators manage and retain sport officials is included

Why Referees Stay in the Game

Current trends indicate the number of qualified sports officials continues to dwindle. Therefore, this research sought to better understand reasons for initial entry, continuation, and potential discontinuation with officiating, while also identifying problematic issues, and potential solutions. Content analysis was utilized to examine five open-ended online survey responses from 2,485 referees. The results indicate that Enjoyable Affiliation (58%) and Remuneration (14%) were key to referees becoming involved in officiating. Those two themes, Enjoyable Affiliation (75%) and Remuneration (14%), were also identified as important to retaining officials. Physical Limitations were mentioned by 58% of the respondents regarding why they plan to discontinue. In terms of the most problematic issues, referees most frequently indicated Abuse (42%) and Administrative Issues (20%). Lastly, findings suggest the best ways to recruit and retain officials are to Provide Mentors and Training (32%), Market to Young People (23%), and Increase Pay (19%). Practical implications and strategies that include attracting more women, underrepresented ethnicities, and young people into sports officiating are provided

Acoustic backscatter from sites in McMurdo Sound from 2014-2015 (McMurdo Predator Prey project)

Dataset: McMurdo Sound acoustic backscatter siteAcoustic echosounder data were collected as part of an ecosystem study in McMurdo Sound, which is located at the southern extent of the Ross Sea in the Southern Ocean. The major goal of this multi-disciplinary project was to assess the influence of top−down forcing (predation) on pelagic zooplankton and fish. Stations were located along the fast ice edge, and along three transects into the fast ice along the eastern side of McMurdo Sound (Ross Island), in the middle of the Sound, and on the western side of the Sound. Krill and fish were sampled between 17 November 2014 – 1 January 2015, both acoustically and visually beneath the fast ice using the tethered SCINI ROV, which was deployed and operated through a 25 cm diameter hole drilled through the sea ice. SCINI contained cameras and thrusters, and towed a sensor package consisting of a WET Labs fluorometer (ECO-AFL/FL) and a single-beam Biosonics 120 kHz DT-X echosounder. Raw acoustic data were analyzed using Echoview software (version 5.3). All acoustic aggregations greater than 4 pings in width were manually delineated, and acoustic energy of the aggregations was integrated into bins of six seconds wide by 1 m in depth. These aggregations were classified as potentially krill or silverfish, based upon ROV visual identification of the targets or, where no visual targets were encountered, by comparing the aggregation target strength, shape, density, and texture and depth to a set of aggregations with positive visual classification. Visual targets were identified to the lowest taxon possible; these observations were used primarily to verify classification of acoustic signals. The echosounder operated at a nominal ping rate of 1 ping s-1; however, this rate was occasionally adjusted if false bottom signals were observed. The general profile of a dive included a surface transect of ~300 m horizontal distance, where the acoustic transducer faced downward, and also a dive to ~120 m if conditions allowed. Echogram data were saved to a depth of 500 m, and background noise was removed. Given the effective range of the transducer of approximately 100 m (resolving -80 dB targets), surveys characterized the upper 200 m of the water column. Finally, all classified volume backscatter values were summed, station means were calculated. Acoustic returns are presented as integrated acoustic energy (volume backscatter strength [Sv], in units of dB re m-1). For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/715512NSF Division of Polar Programs (NSF PLR) PLR-0944747, NSF Division of Polar Programs (NSF PLR) PLR-0944511, NSF Division of Polar Programs (NSF PLR) PLR-094469

Acoustic backscatter from krill and silverfish in McMurdo Sound from 2014-2015

Dataset: McMurdo Sound acoustic backscatter krill and silverfishAcoustic echosounder data were collected as part of an ecosystem study in McMurdo Sound, which is located at the southern extent of the Ross Sea in the Southern Ocean. The major goal of this multi-disciplinary project was to assess the influence of top−down forcing (predation) on pelagic zooplankton and fish. Stations were located along the fast ice edge, and along three transects into the fast ice along the eastern side of McMurdo Sound (Ross Island), in the middle of the Sound, and on the western side of the Sound. Krill and fish were sampled between 17 November 2014 – 1 January 2015, both acoustically and visually beneath the fast ice using the tethered SCINI ROV, which was deployed and operated through a 25 cm diameter hole drilled through the sea ice. SCINI contained cameras and thrusters, and towed a sensor package consisting of a WET Labs fluorometer (ECO-AFL/FL) and a single-beam Biosonics 120 kHz DT-X echosounder. Visual targets were identified to the lowest taxon possible; these observations were used primarily to verify classification of acoustic signals. The echosounder operated at a nominal ping rate of 1 ping s-1; however, this rate was occasionally adjusted if false bottom signals were observed. The general profile of a dive included a surface transect of ~300 m horizontal distance, where the acoustic transducer faced downward, and also a dive to ~120 m if conditions allowed. Echogram data were saved to a depth of 500 m, and background noise was removed. Given the effective range of the transducer of approximately 100 m (resolving -80 dB targets), surveys characterized the upper 200 m of the water column.Raw acoustic data were analyzed using Echoview software (version 5.3). All acoustic aggregations greater than 4 pings in width were manually delineated, and acoustic energy of the aggregations was integrated into bins of six seconds wide by 1 m in depth. These aggregations were classified as potentially krill or silverfish, based upon ROV visual identification of the targets or, where no visual targets were encountered, by comparing the aggregation target strength, shape, density, and texture and depth to a set of aggregations with positive visual classification. Data are provided for every 10 m depth by six second acoustic bin, for each site, with only classified krill or silverfish backscatter in the bins. Zero data is also reported, to allow estimation of density parameters. Acoustic returns are presented as integrated acoustic energy (volume backscatter strength [Sv], in units of dB re m-1). For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/715715NSF Division of Polar Programs (NSF PLR) PLR-0944747, NSF Division of Polar Programs (NSF PLR) PLR-0944511, NSF Division of Polar Programs (NSF PLR) PLR-094469

Structure and Metal Binding Properties of ZnuA, a Periplasmic Zinc Transporter from \u3cem\u3eEscherichia coli\u3c/em\u3e

ZnuA is the periplasmic Zn2+-binding protein associated with the high-affinity ATP-binding cassette ZnuABC transporter from Escherichia coli. Although several structures of ZnuA and its homologs have been determined, details regarding metal ion stoichiometry, affinity, and specificity as well as the mechanism of metal uptake and transfer remain unclear. The crystal structures of E. coli ZnuA (Eco-ZnuA) in the apo, Zn2+-bound, and Co2+-bound forms have been determined. ZnZnuA binds at least two metal ions. The first, observed previously in other structures, is coordinated tetrahedrally by Glu59, His60, His143, and His207. Replacement of Zn2+ with Co2+ results in almost identical coordination geometry at this site. The second metal binding site involves His224 and several yet to be identified residues from the His-rich loop that is unique to Zn2+ periplasmic metal binding receptors. Electron paramagnetic resonance and X-ray absorption spectroscopic data on CoZnuA provide additional insight into possible residues involved in this second site. The second site is also detected by metal analysis and circular dichroism (CD) titrations. Eco-ZnuA binds Zn2+ (estimated K d \u3c 20 nM), Co2+, Ni2+, Cu2+, Cu+, and Cd2+, but not Mn2+. Finally, conformational changes upon metal binding observed in the crystal structures together with fluorescence and CD data indicate that only Zn2+ substantially stabilizes ZnuA and might facilitate recognition of ZnuB and subsequent metal transfer

Recruitment, growth and mortality of an Antarctic hexactinellid sponge, Anoxycalyx joubini.

Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future